Material for waterproofing bridge decks and the like

ABSTRACT

Concrete bridge decks are waterproofed by first applying a primer over sound, dry and clean concrete which forms the bridge deck. A laminated membrane is then installed over the primed concrete surface, the membrane being comprised of reinforced cured and uncured elastomers. The membrane is then heated to the point where the uncured elastomer flows and rolled prior to cooling. A tack coat is then applied over the membrane and a wearing surface, such as asphalt, or the like, applied. 
     The membrane employed is comprised of an upper stratum of a cured elastomer, a reinforcing fabric such as woven fiberglass in the center thereof and a lower stratum of a soft, uncured, form stable elastomer adapted to flow on the application of heat.

This is a division, of application Ser. No. 803,789 filed on June 6,1977 now U.S. Pat. No. 4,151,025.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to a method and material forwaterproofing surfaces such as bridge decks, and the like, and moreparticularly is directed towards a new and improved membrane for use inwaterproofing a bridge deck or the like and the method of installing themembrane.

2. Description of the Prior Art

In the highway construction and maintenance field, serious problems haveexisted for many years with respect to the decks of bridges, overpasses,and the like, especially those constructed with a cement/concrete bedand an asphalt wearing surface. Although such structures are commonlyused, they experience maintenance problems resulting from water leakagepassing through the asphalt into the concrete deck. Such leakagecommonly results in damage to the deck as the result of the waterfreezing and expanding to cause cracks in the concrete during thewinter, and if the highway has been salted, the leaks can result inrusting of reinforcement rods, deck plates and other ferrous metalparts. Also, moisture trapped within the deck or in the inner facebetween the deck and the asphalt may expand when heated, causing theasphalt to lift and crack.

Various attempts have been made to solve the problem but none of thesehas been entirely successful from the standpoint of effectiveness, cost,ease of installation and durability. Various coatings have been employedbut have not provided a durable, fully waterproofed layer over theentire surface. Various sheet materials have also been utilized butthese have been difficult to install and have not bonded well to thedeck and frequently form air pockets when entrained moisture becomesheated during warm periods.

Accordingly, it is an object of the present invention to provide a newand improved membrane for use in waterproofing bridge decks, and thelike. Another object of this invention is to provide an improved methodfor waterproofing bridge decks and the like.

SUMMARY OF THE INVENTION

This invention features the method of waterproofing bridge decks, andthe like, comprising the steps of applying a primer coat to a clean, drydeck, installing a flexible waterproof membrane over the primer coat,the membrane being comprised of an upper stratum of cured elastomer, acenter fabric ply, and a bottom stratum of uncured elastomer. Onceinstalled, the membrane is heated to a point sufficient to cause theuncured stratum of elastomer to flow, then rolled, followed by a tackcoat and a wear surface of asphalt, or the like. This invention alsofeatures a membrane for use in waterproofing a bridge deck, or the like,comprising a threeply, flexible waterproof sheet including an open mesh,flexible center ply, an upper ply of a cured, oil-resistant elastomer,and a bottom ply of a soft, uncured, form stable elastomer adapted toflow upon the application of heat.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow diagram summarizing the sequence of steps involved incarrying out the invention,

FIG. 2 is a perspective view showing a typical installation procedure,

FIG. 3 is a view in perspective showing a section of membrane madeaccording to the invention,

FIG. 4 is a sectional detailed view of the membrane, and,

FIG. 5 is a detailed sectional view of a typical bridge deck membraneinstallation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, the reference character 10 generallyindicates a membrane having particular utility in forming a waterprooflayer on a bridge deck or the like. The membrane is used to waterproofcement/concrete bridge decks prior to a wearing surface being appliedthereto and may also be employed in waterproofing other types ofcement/concrete structures such as roofs, for example. The membrane is aflexible, imperforate, waterproof sheet material typically provided inrolls and, in practice, has a thickness on the order of 1/16". Thethickness is not critical and may be increased or decreased although foruse on bridge decks the thickness should not be less than 0.062".

The membrane is comprised of three strata, namely an upper stratum 12,an inner stratum 14, and a bottom stratum 16. The upper stratum 12, inthe preferred form of the invention, is a cured, oil-resistant elastomerwhich can be any natural or synthetic formulation and preferably it isbased on neoprene rubber, carbon black and reinforcing fillers at arubber hydrocarbon content of not less than 30%. Typically, the curedneoprene stratum 12 has a thickness on the order of 0.008".

The center stratum 14 is a reinforcing fabric material which can be asynthetic material such as polyethylene, polypropolene, polyamide, orpolyester, glass, or a natural product such as cotton. Preferably, thefabric has a relatively open mesh with the interstices being on theorder of 1/8" to 1/16". The fabric may be woven and is coextensive withthe upper stratum 12. A 20×10 glass scrim with a plain weave has beenfound satisfactory.

The bottom stratum 16 provides a soft, form stable heat flowable layerthat can be any natural, synthetic or reclaimed rubber formulation andpreferably it is based on a low unsaturation polyisobutylene-isoprenecopolymer (butyl) or a polyisobutylene (PIB), carbon black, reinforcingand extending fillers, processing oils at a rubber hydrocarbon contentof not less than 20%. Typically, the thickness of the stratum 16 is onthe order of 0.054".

The laminate 10 is preferably unbalanced with the preponderance of thetotal thickness made up of the soft, heat flowable layer 16 with apreferred thickness of 0.045" minimum. The membrane material, which hasbeen found to be particularly satisfactory for bridge deck work has atotal thickness of 0.062" using a plain weave 20×10 glass scrim, and anupper stratum of 0.008" cured neoprene, and a bottom stratum of 0.054uncured butyl.

The membrane is installed on a bridge deck or similar structure by firstpreparing the deck surface which must be sound, dry and clean. In atypical bridge deck structure, a bottom steel plate 18, which may besupported on girders, or the like, carries a relatively thick concretedeck 20. Typically, the cement/concrete deck 20 is reinforced by iron orsteel reinforcing rods 22 laid out in a grid pattern. Starting with asound, dry, clean deck 20, a primer coat 24 is applied over the deck 20and typically at a coverage rate of perhaps 200 sq. feet per gallon ofprimer. The primer in the preferred embodiment is a butyl solvent andserves to make the butyl-concrete interface more compatible and enhancethe bonding action when heat is applied. Once the primer layer 24 hasbeen applied, the membrane 10 is installed.

Typically, the membrane 10 is provided in roll form and is installed bymerely rolling out the membrane in strips of courses, as suggested inFIG. 2. The membrane may be cut to fit as necessary to insure that themembrane is coextensive with the deck surface. The material is soft andmay be cut with shears or a sharp knife to provide a neat fit againstcurbs around drain holes or the like. Once a course of the membrane hasbeen laid out and fitted in place, it is heated to a temperature ofapproximately 175° F. This may be done by various types of heaters, andin the FIG. 2 embodiment a mobile heater 26 is moved across the topsurface of the membrane. The heater 26 preferably is a radiant typeheater using infrared lamps, although other typs of heaters may also beused, and numerous types of heating units are available for thispurpose. In any event, the membrane is heated to about 175° F. at whichtemperature the bottom uncured stratum 16 will flow to an extentsufficient for the stratum 16 to intimately bond with the top surface ofthe deck 20, forming an extremely tight integument which is highlywaterproof and tightly secured to the deck.

While the membrane is still in this heated condition, it is presseddown, preferably by means of a hand roller 28 to insure that all airbubbles are rolled out from between the deck and the membrane before thematerial has cooled. Once one course of membrane has been installed, asecond course or strip is applied. The same sequence is followed with aprimer coat being first applied, followed by the laying out of themembrane. The adjacent courses should overlap one another preferably byat least 2" to insure a continuous membrane surface over the deck. Thesecond course, once installed, is heated and rolled and successivecourses added until the deck is fully covered.

Once the membrane has been fully installed, a tack coat is applied ontop of the membrane. The tack coat in the preferred embodiment is anasphalt emulsion typically comprised of 65% asphalt and 45% emulsifiersand water by weight. Once the tack coat 30 has been applied, the wearingsurface, such as a bituminous concrete overlay 32, is placed directly ontop of the tack coated membrane. The bituminous concrete is installed inaccordance with usual practice. Typically, the hot top is applied atabout 300° F. When installing the membrane, ambient temperaturepreferably should be at least 45° F. in order to allow the membrane tobe properly heated and to retain heat long enough for the membrane to berolled to remove air bubbles.

The membrane made in accordance with the present invention ischaracterized by a puncture resistance of 67.7-72.2 per ASTM EL 54. Themembrane will pass the cold crack at 15° F. per ASTM D146. The membraneis sufficiently tough that it does not require any protective courseprior to the overlay of bituminous concrete and it may have a trackpaver riding directly on its surface.

While the invention has been described with particular reference to theillustrated embodiments, numerous modifications thereto will appear tothose skilled in the art. For example, membrane may be used forwaterproofing other structures such as roofs of buildings of varioustypes, or other structures where a highly efficient waterproofingsurface is required.

Having thus described the invention, What I claim and desire to obtainby Letters Patent of the United States is:
 1. A membrane for use inwaterproofing bridge decks or the like, comprising(a) a first ply of acured flexible elastomer, defining one side of said membrane, (b) asecond ply of an uncured flexible elastomer, defining the opposite sideof said membrane, and (c) a third ply of flexible fabric of open meshweave laminated between said first and second plies, (d) said second plybeing a soft, uncured, form stable elastomer adapted to flow whenheated.
 2. A membrane, according to claim 1, wherein said first ply is aneoprene based rubber.
 3. A membrane, according to claim 1, wherein saidsecond ply is a butyl based rubber.
 4. A membrane, according to claim 3,wherein said second ply is selected from a group consisting of lowunsaturated polyisobutylene, isoprene copolymer and polyisobutylene,each of said group being combined with carbon black, reinforcing andextending fillers, and processing oils.
 5. A membrane, according toclaim 1, wherein said third ply is selected from a group consisting ofpolyethylene, polypropylene, polyamide, polyester, fiberglass andcotton.
 6. A membrane, according to claim 3, wherein said second ply issubstantially thicker than said first ply.
 7. A membrane, according toclaim 1, wherein said second ply is of a material adapted to flow whenheated to approximately 175° F.